The present invention pertains to an AlRu sputtering target, and particularly to an AlRu sputtering target favorable in forming films for hard disks, as well as the manufacturing method thereof.
In recent years, in order to improve the data density of hard disks, numerous materials are being considered. Among such materials, a medium employing a multilayer film having AlRu as its constituent element (composed of an element having a sandwich structure with a magnetic layer) is known to significantly improve the recording density, and it is said that in the near future it will be possible to store 100 gigabits of data per square inch of the disk area.
In order to form a multilayer film with the sputtering method, most commonly, targets composed of a positive electrode and a negative electrode are made to face each other, and high voltage is applied between the substrate and target under an inert gas atmosphere in order to generate an electric field.
As a result of applying the high voltage described above, employed is the fundamental principle in which plasma is formed upon the atoms ionized at such time colliding with the inert gas, the positive ions within this plasma colliding with the target (negative electrode) surface and discharging the atoms structuring the target, whereby the film is formed by the discharged atoms adhering to the opposing substrate surface.
As this type of sputtering method, there are the high frequency sputtering (RF) method, magnetron sputtering method, DC (direct current) sputtering method, among others, and these methods are suitably used in accordance with the target material or conditions for forming the film.
In a conventional AlRu sputtering target, there is a particular problem in that the target material is not even, and that it contains a high content of oxygen.
When employing this kind of target, there are problems in that numerous particles will be generated upon forming the sputtering film, unevenness of the film will further generate a defective deposition product, and the yield ratio will decrease.
As the usage conditions of the AlRu sputtering target, Al-50 at % Ru is employed compositionally, but since the melting temperature of this composition is 2000° C. or higher, it is difficult to employ a melting-casting product as a target from the perspective of manufacturing costs.
Therefore, equimolar Al and Ru powders are used, and the sintered body target of Al-50 at % Ru obtained by mixing and sintering such powders is employed.
The SEM image, Ru distribution image, Al distribution image and O distribution image of a conventional Al-50 at % Ru sintered body target surface are shown in FIG. 5, FIG. 6, FIG. 7 and FIG. 8, respectively.
As shown in FIG. 5, the existence of numerous large grains can be acknowledged in the SEM image. In terms of chemical composition, Al, Ru, and Al—Ru alloy are dispersed unevenly.
Moreover, as shown in FIG. 6 and FIG. 7, it is evident that Ru and Al are significantly segregated. Further as shown in FIG. 8, oxygen is distributed in a large amount and in an uneven manner.
Accordingly, upon manufacturing an Al-50 at % Ru sintered body target, when simply employing equimolar Al and Ru powders, this will result in high oxygen content and uneven textures, thereby causing the generation of particles. In addition, with this kind of conventional manufacturing method, there is a problem in that the oxygen content cannot be reduced from the sintered body target.